1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
|
/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_linear_interp_q15.c
* Description: Q15 linear interpolation
*
* $Date: 23 April 2021
* $Revision: V1.9.0
*
* Target Processor: Cortex-M and Cortex-A cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "dsp/interpolation_functions.h"
/**
@ingroup groupInterpolation
*/
/**
* @addtogroup BilinearInterpolate
* @{
*/
/**
* @brief Q15 bilinear interpolation.
* @param[in,out] S points to an instance of the interpolation structure.
* @param[in] X interpolation coordinate in 12.20 format.
* @param[in] Y interpolation coordinate in 12.20 format.
* @return out interpolated value.
*/
q15_t arm_bilinear_interp_q15(
arm_bilinear_interp_instance_q15 * S,
q31_t X,
q31_t Y)
{
q63_t acc = 0; /* output */
q31_t out; /* Temporary output */
q15_t x1, x2, y1, y2; /* Nearest output values */
q31_t xfract, yfract; /* X, Y fractional parts */
int32_t rI, cI; /* Row and column indices */
q15_t *pYData = S->pData; /* pointer to output table values */
uint32_t nCols = S->numCols; /* num of rows */
/* Input is in 12.20 format */
/* 12 bits for the table index */
/* Index value calculation */
rI = ((X & (q31_t)0xFFF00000) >> 20);
/* Input is in 12.20 format */
/* 12 bits for the table index */
/* Index value calculation */
cI = ((Y & (q31_t)0xFFF00000) >> 20);
/* Care taken for table outside boundary */
/* Returns zero output when values are outside table boundary */
if (rI < 0 || rI > (S->numCols - 2) || cI < 0 || cI > (S->numRows - 2))
{
return (0);
}
/* 20 bits for the fractional part */
/* xfract should be in 12.20 format */
xfract = (X & 0x000FFFFF);
/* Read two nearest output values from the index */
x1 = pYData[((uint32_t)rI) + nCols * ((uint32_t)cI) ];
x2 = pYData[((uint32_t)rI) + nCols * ((uint32_t)cI) + 1];
/* 20 bits for the fractional part */
/* yfract should be in 12.20 format */
yfract = (Y & 0x000FFFFF);
/* Read two nearest output values from the index */
y1 = pYData[((uint32_t)rI) + nCols * ((uint32_t)cI + 1) ];
y2 = pYData[((uint32_t)rI) + nCols * ((uint32_t)cI + 1) + 1];
/* Calculation of x1 * (1-xfract ) * (1-yfract) and acc is in 13.51 format */
/* x1 is in 1.15(q15), xfract in 12.20 format and out is in 13.35 format */
/* convert 13.35 to 13.31 by right shifting and out is in 1.31 */
out = (q31_t) (((q63_t) x1 * (0x0FFFFF - xfract)) >> 4U);
acc = ((q63_t) out * (0x0FFFFF - yfract));
/* x2 * (xfract) * (1-yfract) in 1.51 and adding to acc */
out = (q31_t) (((q63_t) x2 * (0x0FFFFF - yfract)) >> 4U);
acc += ((q63_t) out * (xfract));
/* y1 * (1 - xfract) * (yfract) in 1.51 and adding to acc */
out = (q31_t) (((q63_t) y1 * (0x0FFFFF - xfract)) >> 4U);
acc += ((q63_t) out * (yfract));
/* y2 * (xfract) * (yfract) in 1.51 and adding to acc */
out = (q31_t) (((q63_t) y2 * (xfract)) >> 4U);
acc += ((q63_t) out * (yfract));
/* acc is in 13.51 format and down shift acc by 36 times */
/* Convert out to 1.15 format */
return ((q15_t)(acc >> 36));
}
/**
* @} end of BilinearInterpolate group
*/
|
